Process of coking high volatile coal involving incorporation therein of a limited amount of blast furnace flue dust



Patented June 21, 1949 PROCESS OF COKING HIGH VOLATILE COAL INVOLVING INCORPORATION THEREIN OF A LIMITED AMOUNT OF BLAST FURNACE FLUE DUST George E. Brandon, East Orange, N. J., assignor to Allied Chemical & Dye Corporation, a corporation of New York No Drawing. Application October 23, 1945,

. Serial No. 624,083

2 Claims. (Cl. 202-34) This invention relates to the coking of coal -and more particularly to the coking of high volatile coal in admixture with a low volatile coal, to produce coke suitable for use in metallurgical operations. v

It is well known that large deposits of high volatile coal are available, particularly in the central and western parts of the United States, which coal when sublected to coking yields a poor grade of coke in that the coke is weak and crumbly or in the form of flnes.

The prior art discloses a number of suggestiors for improving the quality of coke by treating coal prior to coking. Thus, for example, Patent No. 486,100 of November 15, 1892, discloses the addition of lime to coal prior to coking to produce a harder and denser coke. Patent No. 1,308,754 of July 18, 1919, discloses the addition of pitch and coke breeze to coal and coking the mixture to improve the hardness and toughness of the coke. Patent No. 1,665,665 of April 10, 1928, discloses the addition of iron carbonate to tar such as coal tar, admixing this mixture with pulverized coal and subjecting the resultant coal mixture to a low temperature (about 500 C.) dry carbonization to produce a coke which is alleged to be suitable for blast furnace use. To the best of my knowledge and belief, none of these prior processes have been found satisfactory commercially.

It is an object of this invention to provide a process for coking high volatile coal in admixture with low volatile coal, to produce an improved coke product suitable for use in blast furnace operation. Another object is to provide such improved coke using a material for admixture with the high volatile coal prior to coking which material is readily available at steel mills. Such mills generally have operating in conjunct on therewith a by-product coke plant; hence t e process of this invention is economical to carrv out particularly in that it makes use of readilv available materials. Other objects and advantages of this invent on will be apparent from the fo lowin detailed description thereof.

In accordance with this invention a hi h volatile coal in admixture with a low volatile coal is m xed with a minor amount of blast furnace flue dust and the mixture subiected to high temperature coking in the coking chambers of any f t e well known types of bv-product coke oven b t erie e. 2.. the Wilnutte Coke Oven Battery.

Bv h h volatile coal is meant bituminous coal, lar e deposits of which are found. for example, in the central and western part of the United States containing from 27% to 38% volatiles. All percentage figures given in the specification and claims are on a weight basis. By low volatile coal is meant bituminous coal containing from 14% to 23% volatiles.

In accordance with a preferred embodiment of this invention bituminous coal may be mixed with the blast furnace flue dust in the proportion of- 90% to 97% coal to 3% to 10% flue dust preferably about 95% coal and about 5% flue dust. The low and high volatile coals are preferably mixed in proportions so that the amount of high volatile coal preponderates, i. e., less than 50% low volatile coal is incorporated in the coal mixture. Preferably, however, at least 15% low volatile coal is incorporated in the mixture. The coal is mixed with the flue dust, the mixture ground in a suitable grinding mill so that about 80% passes a A, inch mesh screen and the resultant ground mixture subjected to high temperature coking, or the mixture of high and low volatile coals may be ground first to the particle size above indicated, -mixed with the flue dust and the resultant mixture subjected to high temperature coking.

Any high-volatile bituminous coal may be mixed with low-volatile coal, flue dust added, the resultant mixture ground, if desired, to the particle size above indicated and then subjected to high temperature coking. The coking temperature to which the mixture is sub eeted should be within the range of 1600" to 2200 F. preferably 1800-2000 F. The time of coking should be the same as that usually employed in coking coal, when the coking is carried out in a modern coke oven battery.

The flue dust used is recovered from b a t furnace o eration by elim nating t e same from the blast furnace gas by means of dry dust catchers or washers or both as is conventional practice in the operation of blast furnaces. Heretofore the blast furnace flue dust was dis osed of by sintering it and charging t e sintered product into the blast furnace. O erating in accordance with this invention the recovered flue dust as such, i. e., without sintering. is mixed with the coal and eventually the major portion thereof is returned to the blast furnace incorporated in the improved coke which is charged into the furnace. Thus this invention eliminates the necessity for sintering the flue dust and improves the efficiency of the operation of the-blast furnace due to the better ouality of coke used therein.

The flue dust used in practicing this invention may'contain from 2% to 10% carbon, 2% to 5% a v 3 lime, 3% to 12%- silica', 2% to 3% alkali in the form of sodium and potassium salts chiefly the silicates and from 70% to 90% iron oxides (Fe-a: and FeO). Typical analyses of blast furnace flue dust which may be used in the practice of this invention are as follows.

Analysis I Analysis 11 Per cent Per cent Silica 6. 8 11 Carbon 5. 2 6. 35 Lima..- 4. 8 2. 4 Alkali 2 2 Moisture 6 Iron Oxides (FeeO and FeO) 81. 2 73. 25

In the above tables the alkali is in the form of sodium and potassium salts chiefly the silicates. In operation this invention has been found to result in coke in the form of hard, strong lumps,

the majority of which are of relatively large size and free from excessive fines. The strength of the coke and the size of the lumps has been found markedly improved as compared with the strength and size of lumps produced-by coking high volatile coal without added flue dust and also as compared with coke produced by coking a mixture of high and-low volatile coals, without added flue dust. That this invention results in larger lumps of coke is evident from Tables I and 11 below. Table I gives a screen analysis of the size of coke particles produced by coking a mixture of 80% high volatile coal 15% low volatile coal and flue dust. Table II gives the screen analysis of coke produced by coking amixture of 80% high volatile and 20% low volatile coal without flue dust, the coal coked being of the same type in both cases.

Table I Size of Coke Lumps v Coke of this Table II Invention Percent Percent Exceeding 5/2..-. 50 16. 7

From 4" to 5". 27 v 26 From 3" to 4". l2 30. 7 From 2" to 3"...- 6.8 19.8 Less than 2".....---.-.--, 4.2 7.8

The coke screen analysis of which is given in- Table I above, which coke it will be noted was made in accordance with this invention, was found to be of markedly increased strength as compared with the coke the screen analysis of which is given in Table II.

Thus it will be noted the coke produced in accordance with this invention, is stronger and in larger lumps than coke heretofore made from i hvolatile coal. Furthermore the invention involving .as it does the admixture of blast furnace flue dust with the coal utilizes a material which ..is readily available where the coke is produced since by-product coke oven batteries are frebe interpreted as illustrative and not in a, limiting sense.

What is claimed is: 1. A process of making coke which comprises mixing'approximately 80% bituminous coal con taining from 27% to 38% volatiles with approximately 15% bituminous coal containing from 14% to 23% volatilesand approximately 5% blast furnace flue dust and subjecting the resultant mixture to high temperature coking.

2. A process of making coke, which comprises producing a mixture consisting of from 90% to 97% bituminous coal and from 3% to 10% blast furnace 'flue dust, the bituminous coal constituents of said mixture consisting of both high volatile bituminous coal containing from 27% to 38% volatiles and low volatile bituminous coal containin from 14% to 23% volatiles, the amount of high volatile bituminous coal in said mixture preponderating' over the amount of said low volatile bituminous coal and the amount of said low volatile bituminous coal being at least 15% of 1 the mixture and subjecting the mixture to high temperature coking.

' GEORGE E. BRANDON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 486,100 Fronheiser Nov. 15, 1892 945,331 Koppers Jan. 4, 1910 1,098,359 Franch May 26, 1914 FOREIGN PATENTS Number Country Date 368,881 Great Britain Mar. 1'7, 1932 288,264 Germany Nov. 15, 1928 

